In a double flywheel, such as that described in French published patent application FR 2 571 461A, the resilient means are housed on a pitch circle of larger diameter, and the angular displacement between the two masses in relative rotation is large. Consequently the resilient means are subjected to very high compressing forces, especially under the action of centrifugal force.
In order to reduce the wear and the noise resulting from this high deformation of the resilient means, the resilient means may be conceived as being housed within a sealed cavity which is filled with a lubricating fluid.
It may also be desirable to use a viscous damping means with a view to an effective reduction in unwanted vibrations.
If the lubricating fluid is used in the viscous damper, a problem arises from the characteristics of the fluid, since one single fluid cannot, in general, satisfactorily be used both for lubricating the resilient means and for the purposes of viscous damping.